1. Field of the Invention
The present invention relates generally to lasers, especially those utilized in gyro assemblies, and more particularly, to the cathode constructions found in such assemblies.
2. Description of the Prior Art
Strapped down laser gyros have been proposed as a substitute for the gimbol mounted gyros presently utilized in inertial navigational systems.
In laser gyros, particularly those proposed for navigational systems, it is preferable that the laser gyro life cycles be as long as other components in the systems.
Heretofore, laser gyros have not had a long lifespan because of the short lifetimes of the laser cathodes. Initially, the prior art lasers were made of bare metals. The shortcoming with such a cathode construction was that the cathode, being negatively charged, would attract the positive ions in the plasma and create a sputtering problem. To overcome this problem, later cathodes have been made with a thin layer of oxide covering the metal surface. The advantage of this construction is that the oxide layer is more capable of withstanding ion bombardment while still being able to provide electron conduction through the layer at reasonable discharge voltages.
The most widely used prior art cathode of this type has been made of aluminum coated with a thin layer of oxide. During the manufacturing process the layer of aluminum oxide is formed naturally by exposing the aluminum cathode to an oxygen plasma with the aluminum cathode connected as the cathode in the circuit. The thin layer of oxide is formed due to the pressure of oxygen and the heating effect of the plasma.
Cathodes utilized in gyro lasers invariably have sharp edges and machining irregularities formed on the emitting surface. These areas tend to create high electric fields. The shortcoming with the above-mentioned method is that an even layer of oxide is formed over the entire cathode structure including the high field areas. As a result, the electron conduction is greater through these areas, thereby creating hot spots and rapid cathode degradation.